bpf: correct neg and neg32 instruction encoding

bpf: correct neg and neg32 instruction encoding

The neg/neg32 BPF instructions always use BPF_SRC_K (=0) in their header
source bit, despite operating on registers.  If BPF_SRC_X (=1) is set,
the instructions are rejected by the kernel.

Because of this there are also no neg/neg32 instructions which operate
on immediates, so remove them.

bd434cc4d94ec3d2f9fc1e7c00c27b074f962bc1 was a similar fix in the old
CGEN-based port, but was not carried forward in the new port.

include/
	* opcode/bpf.h (enum bpf_insn_id): Remove spurious entries
	BPF_INSN_NEGI and BPF_INSN_NEG32I.

opcodes/
	* bpf-opc.c (bpf_opcodes): Remove erroneous NEGI and NEG32I
	instructions.

gas/
	* doc/c-bpf.texi (BPF Instructions): Remove erroneous neg and
	neg32 instructions operating on immediates.
	* testsuite/gas/bpf/alu.s: Adapt accordingly.
	* testsuite/gas/bpf/alu.d: Likewise.
	* testsuite/gas/bpf/alu-be.d: Likewise
	* testsuite/gas/bpf/alu32.s: Likewise.
	* testsuite/gas/bpf/alu32.d: Likewise.
	* testsuite/gas/bpf/alu32-be.d: Likewise.
	* testsuite/gas/bpf/alu-pseudoc.s: Likewise.
	* testsuite/gas/bpf/alu-pseudoc.d: Likewise.
	* testsuite/gas/bpf/alu-be-pseudoc.d: Likewise.
	* testsuite/gas/bpf/alu32-pseudoc.s: Likewise.
	* testsuite/gas/bpf/alu32-pseudoc.d: Likewise.
	* testsuite/gas/bpf/alu32-be-pseudoc.d: Likewise.